The invention relates to the field of double-plate combiners for a head-up visor, and especially for a head-up visor mounted in the cockpit of an aircraft, preferably of the airplane type. The function of the combiner for a head-up visor is generally to superimpose on the external scene viewed by the pilot the simultaneous display of synthetic images preferably collimated at infinity. The synthetic images intended to be superimposed on the external scene via the combiner are generated by the head-up visor. A double-plate combiner is a type of combiner comprising two plates and having the advantage, with respect to a combiner with a single plate, of increasing the on-site size of the instantaneous field in which the synthetic images intended to be viewed by the pilot can be displayed.
According to a prior art, a double-plate combiner exists, on the one hand, whose two substantially parallel plates are held by a pair of spacers, the mid-plane of which is orthogonal to the mid-plane of the plates, and, on the other hand, of which the dimension, from one spacer to the other, is the same for both plates. A drawback of this prior art is the fact of presenting a visual mask which is annoying for the pilot.
A first solution (not claimed) would consist in replacing the opaque material forming the plate holding structure with a material which is transparent in the visible region.
A second solution (not claimed) would consist in using spacers which are not very bulky, for example thin and with holes, and whose actual structure would present a visual mask which is small enough.
A third solution (claimed) consists of a novel structure for the combiner, in which the relative size of the plates and the inclination of the spacers of the plate holding structure are especially modified, so as to be able both, on the one hand, to provide a stable and rigid hold for the two plates in a vibrating environment which could be severe and, on the other hand, to substantially decrease the size of the visual mask connected to the plate holding structure, which visual mask is annoying for the pilot. The novel structure for the combiner according to the invention also makes it possible to attenuate or even to remove the unwanted reflections taking place on some surfaces of the spacers in the combiners of the prior art, by virtue of the novel inclination of the spacers of the holding structure. These unwanted reflections on the spacers may also be problematic for the pilot.
According to the invention, provision is made for a double-plate combiner for a head-up visor, comprising two substantially flat plates, substantially parallel to each other and held fixedly together by a holding structure which comprises a central baseplate, two side flanks connected to the central baseplate, two spacers respectively connected to the side flanks and tightly holding the two plates between them, an outer plate being tightly held between the free ends of the spacers, an inner plate being tightly held between the ends, connected to the side flanks, of the spacers, the assembly consisting of the plates, the side flanks and the spacers having a plane of symmetry substantially orthogonal to the mid-plane of the plates, characterized in that the dimension, from one spacer to the other, of the outer plate is greater than the dimension, from one spacer to the other, of the inner plate, and in that the mid-plane of each spacer is not orthogonal to the mid-plane of the plates.